Thoughts on Perl and Emacs, technology and writing

Reliable Windows Software Without Fork

How does windows work without fork? So many things start with a call to fork: starting a new process (fork/exec), creating a daemon, creating independent tasks within one program…

The nice thing about all of these things is, if a new process goes bad, it probably won’t take out the parent process. You don’t get the same safety with a thread. Therefore, fork is the basis of a lot of my reliable software.

I’m fairly confident that windows doesn’t have anything similar to fork. Otherwise the perl fork emulation could simply wrap whatever windows has. Sadly it doesn’t quite work that nicely.

While the emulation is designed to be as compatible as possible with the real fork() at the level of the Perl program, there are certain important differences that stem from the fact that all the pseudo child "processes" created this way live in the same real process as far as the operating system is concerned.

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If the parent process is killed (either using Perl’s kill() builtin, or using some external means) all the pseudo-processes are killed as well, and the whole process exits.

I have been approaching this problem of reliable windows software from too low a level. Rather than copying what I do on Unix and start with fork (using Perl more or less as my OS wrapper), I now use web servers to manage my processes.